U.S. patent application number 15/930337 was filed with the patent office on 2020-08-27 for integrated supercritical water and steam cracking process.
The applicant listed for this patent is Saudi Arabian Oil Company. Invention is credited to Essam A. AL-SAYED, Abdullah T. ALABDULHADI, Mohammad A. ALABDULLAH, Ali M. ALSOMALI, Ki-Hyouk CHOI, Gonzalo Feijoo MARTINEZ.
Application Number | 20200270535 15/930337 |
Document ID | / |
Family ID | 1000004816177 |
Filed Date | 2020-08-27 |
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United States Patent
Application |
20200270535 |
Kind Code |
A1 |
CHOI; Ki-Hyouk ; et
al. |
August 27, 2020 |
INTEGRATED SUPERCRITICAL WATER AND STEAM CRACKING PROCESS
Abstract
A method for producing a supercritical water (SCW)-treated
product is provided. The method comprising the steps of introducing
a crude oil stream and a water stream to a supercritical water
process, wherein the crude oil stream can undergo conversion
reactions to produce the supercritical water (SCW)-treated product,
wherein the SCW-treated product includes an increased paraffin
concentration as compared to crude oil stream. The method further
includes the step of introducing the SCW-treated product to a steam
cracking process, wherein the SCW-treated product can undergo
conversion reactions to produce furnace effluent.
Inventors: |
CHOI; Ki-Hyouk; (Dhahran,
SA) ; ALABDULHADI; Abdullah T.; (Dhahran, SA)
; MARTINEZ; Gonzalo Feijoo; (Dhahran, SA) ;
ALSOMALI; Ali M.; (Dhahran, SA) ; ALABDULLAH;
Mohammad A.; (Dhahran, SA) ; AL-SAYED; Essam A.;
(Al-Khobar, SA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Saudi Arabian Oil Company |
Dhahran |
|
SA |
|
|
Family ID: |
1000004816177 |
Appl. No.: |
15/930337 |
Filed: |
May 12, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15920099 |
Mar 13, 2018 |
10703999 |
|
|
15930337 |
|
|
|
|
62471016 |
Mar 14, 2017 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10G 31/08 20130101;
C10G 9/36 20130101; C10G 53/02 20130101; C10G 69/06 20130101; C10G
55/04 20130101; C10G 51/023 20130101 |
International
Class: |
C10G 69/06 20060101
C10G069/06; C10G 53/02 20060101 C10G053/02; C10G 51/02 20060101
C10G051/02; C10G 55/04 20060101 C10G055/04; C10G 31/08 20060101
C10G031/08; C10G 9/36 20060101 C10G009/36 |
Claims
1. An apparatus for upgrading a crude oil stream, the apparatus
comprising: a pre-reaction stage configured to produce a mixed
stream from the crude oil stream and a water stream, the
pre-reaction stage comprising a feed pump, a feed heater, a water
pump, a water heater, and a mixer; a reaction stage fluidly
connected to the pre-reaction stage, the reaction stage comprising:
a convection section of a furnace fluidly connected to the
pre-reaction stage, the convection section configured to subject
the mixed stream to conversion reactions to produce convection
upgraded stream, wherein the convection upgraded stream is at a
temperature between the critical temperature of water and
500.degree. C., a supercritical reactor fluidly connected to the
convection section, wherein the supercritical reactor is configured
to subject the convection upgraded stream to one or more conversion
reactions to produce a reactor effluent, wherein the supercritical
reactor is maintained at a temperature between 380.degree. C. and
450.degree. C. and a pressure between 23 MPa and 35 MPa, a
radiation section of the furnace fluidly connected to the
convection section of the furnace, wherein the radiation section is
configured to upgrade a second fraction of components of an
SCW-treated and diluents to produce a furnace effluent, where the
second fraction of components of the SCW-treated product are
subject to radical-mediated reactions; and a post-reaction stage
fluidly connected to the reaction stage, the post-reaction stage
configured to separate the reactor effluent to produce the
supercritical water (SCW)-treated product, wherein the SCW-treated
product comprises an increased paraffin concentration as compared
to the crude oil stream, wherein the SCW-treated product comprises
an amount of water.
2. The system of claim 1, wherein a first fraction of the
SCW-treated product is upgraded in the convection section of the
furnace.
3. The system of claim 1, wherein the post-reaction stage is
configured to adjust the amount of water in the SCW-treated
product.
4. The system of claim 1, further comprising an intermediate unit
fluidly connected to the post-reaction stage, the intermediate unit
configured to produce a product stream.
5. The system of claim 4, wherein the intermediate unit is selected
from the group consisting of a hydrotreating process, a
distillation process, and a thermal conversion process.
6. The system of claim 4, wherein the intermediate unit is a
hydrotreating process and wherein the product stream is a
hydrotreating process (HTP)-product.
7. The system of claim 6, wherein the crude oil stream comprises a
concentration of a vacuum residue fraction that is greater than 20
wt %, wherein the crude oil stream comprises a total sulfur content
that is greater than 1.5 wt % sulfur.
8. The system of claim 6, wherein the amount of water in the
SCW-treated product is less than 1,000 wt ppm.
9. The system of claim 4, wherein the intermediate unit is a
distillation process, further wherein the product stream is a
distilled product.
10. The system of claim 9, wherein the distillation process is
selected from the group consisting of an atmospheric distillation
unit, a vacuum distillation unit, and a combination thereof.
11. The system of claim 8, wherein the crude oil stream comprises a
vacuum residue fraction that is greater than 20 wt %.
12. The system of claim 9, wherein the SCW-treated product
comprises a concentration of a vacuum residue fraction that is
greater than 20 wt %.
13. The system of claim 9, wherein a cut point of distillation of
the distillation process is between 650.degree. F. and 1050.degree.
F.
14. The system of claim 4, wherein the intermediate unit is a
thermal conversion process, further wherein the product stream is a
thermal liquid product.
15. The system of claim 14, wherein the thermal conversion process
is selected from the group consisting of a coking process and a
visbreaking process.
16. The system of claim 14, wherein the crude oil stream comprises
a concentration of a vacuum residue fraction that is greater than
20 wt %.
17. The system of claim 14, wherein the thermal liquid product
comprises a concentration of a vacuum residue fraction that is less
than 5 wt %.
18. The system of claim 1, wherein: the feed pump is configured to
increase a pressure of the crude oil stream to produce a
pressurized oil, wherein the pressurized oil is at a pressure at or
greater than the critical pressure of water; the feed heater
fluidly connected to the feed pump, the feed heater configured to
heat the pressurized oil to a temperature at or less than
150.degree. C. to produce a hot oil stream; the water pump
configured to increase a pressure of water stream to a pressure at
or greater than the critical pressure of water to produce a
pressurized water; the water heater fluidly connected to the water
pump, the water heater configured to heat the pressurized water to
a temperature at or greater than the critical temperature of water
to produce a supercritical water stream; and the mixer fluidly
connected to the feed heater and the water heater, the mixer
configured to mix the hot oil stream and the supercritical water
stream to produce the mixed stream.
Description
RELATED APPLICATIONS
[0001] This application is a divisional application of U.S. patent
application Ser. No. 15/920,099 filed on Mar. 13, 2018, which is
related to and claims priority from U.S. Pat. App. No. 62/471,016
filed on Mar. 14, 2017. For purposes of United States patent
practice, this application incorporates the contents of both the
provisional application and non-provisional application by
reference in their entirety.
TECHNICAL FIELD
[0002] Disclosed are methods for upgrading petroleum. Specifically,
disclosed are methods and systems for upgrading petroleum using an
integrated supercritical water and steam cracking process.
BACKGROUND
[0003] Conventionally, ethane and naphtha (boiling point less than
200 degrees Celsius (deg C.)) can be used to produce light olefins,
such as ethylene and propylene by a steam cracking process.
Naphtha, such as straight run naphtha, can be a paraffin-rich
hydrocarbon stream. However, the naphtha fraction in crude oil can
be limited to between 10 and 30 percent by volume (vol %).
Conventional steam cracking processes can be used to process gas
oil. Gas oil refers to hydrocarbons with a boiling point between
200 deg C. and 565 deg C., where light gas oil has a boiling point
between 200 deg C. and 370 deg C., and where vacuum gas oil has a
boiling point between 200 deg C. and 565 deg C. Due to the presence
of heavier molecules steam cracking of gas oil results in a reduced
yield of ethylene and propylene and greater coking rates relative
to steam cracking of naptha.
[0004] In petroleum-based crude oils, various types of molecules
are present. Per their chemical structure, molecules can be
classified as paraffin, olefin, naphthene (a cyclic paraffin), and
aromatic, which can be indicated by an oil composition's PONA
number. Of the molecules, it is most efficient to convert paraffins
to light olefins, with n-paraffins being more effectively converted
than iso-paraffins, and for this reason n-paraffins can be
preferred. Aromatics, such as benzene and toluene, are stable at
high temperatures, have a low hydrogen to carbon ratio, and are
known to be an effective precursor for coke formation. The
stability of aromatics can be contributed to the carbon-carbon bond
energies of the aromatic carbon, as compared to the carbon-carbon
bond energies of paraffinic carbons. For these reasons, aromatics
are difficult to convert and are not a good source for producing
light olefins. Naphthenes as a source material are more difficult
to convert than paraffins, but easier to convert than aromatics.
Olefinic compounds are generally cracked in a steam cracker to
produce light paraffins and olefins while aromatics with
longer-chained olefins are formed through cyclization followed by
dehydrogenation reactions. Thus, a feedstock for a steam cracking
process preferably contains a majority n-paraffins, followed by
iso-paraffins, and naphthenes with little or no olefins or
aromatics.
[0005] Steam cracking processes cannot effectively process heavy
fractions that contain asphaltene. Steam cracking asphaltene can
produce coke, which can result in plugging of the process
lines.
[0006] Some pre-treatment steps can be taken to make gas oil or
other heavy oils suitable for use as a steam cracking process
feedstock. Pre-treatment approaches can include hydrotreatment,
thermal conversion, extraction, and distillation. Extraction
processes can include a solvent deasphalting process. However,
these processes produce liquid yields of less than 80 percent by
volume, resulting in analogous low product recovery from the steam
cracking process. In addition, pre-treatment processes can increase
the cost per barrel to the resultant products.
SUMMARY
[0007] Disclosed are methods for upgrading petroleum. Specifically,
disclosed are methods and systems for upgrading petroleum using an
integrated supercritical water and steam cracking process.
[0008] In a first aspect, a method for producing a supercritical
water (SCW)-treated product is provided. The method includes the
steps of introducing a mixed stream to a convection section of a
furnace to produce a convection upgraded stream, where the
temperature of the convection upgraded stream is between the
critical temperature of water and 500 deg C., where conversion
reactions occur in the convection section, introducing the
convection upgraded stream to a supercritical reactor to produce a
reactor effluent, where the supercritical reactor is maintained at
a temperature between 380 deg C. and 450 deg C. and a pressure
between 23 MPa and 35 MPa, wherein one or more conversion reactions
occur in supercritical reactor, and introducing the reactor
effluent to a post-reaction stage to produce the SCW-treated
product, wherein the SCW-treated product has an increased paraffin
concentration as compared to the crude oil stream, wherein the
SCW-treated product include an amount of water.
[0009] In certain aspects, the post-reaction stage can be
configured to adjust the amount of water in the SCW-treated
product. In certain aspects, the method further includes the step
of introducing the SCW-treated product to the convection section of
the furnace to produce a furnace effluent, where the SCW-treated
product is subjected to one or more conversion reactions, where the
furnace effluent is withdrawn from a radiation section of the
furnace. In certain aspects, the method further includes the steps
of introducing the SCW-treated product to an intermediate unit to
produce a product stream, and introducing the product stream to the
convection section of the furnace to produce a furnace effluent,
where the product stream is subjected to one or more conversion
reactions, where the furnace effluent is withdrawn from a radiation
section of the furnace. In certain aspects, the intermediate unit
can be selected from the group consisting of a hydrotreating
process, a distillation process, and a thermal conversion process.
In certain aspects, the intermediate unit is a hydrotreating
process and the product stream is a hydrotreating (HTP)-product. In
certain aspects, the crude oil stream includes a concentration of a
vacuum residue fraction that is greater than 20 percent by weight
(wt %) and a total sulfur content that is greater than 1.5 wt %
sulfur. In certain aspects, the amount of water in the SCW-treated
product is less than 1,000 parts-per-million by weight (wt ppm). In
certain aspects, the method further includes the step of
introducing hydrogen gas to the hydrotreating process. In certain
aspects, the intermediate unit is a distillation process and the
product stream is a distilled product. In certain aspects, the
distillation process is selected from the group consisting of an
atmospheric distillation unit, a vacuum distillation unit, and a
combination thereof. In certain aspects, the SCW-treated product
includes a concentration of the vacuum residue fraction that is
greater than 20 wt %. In certain aspects, a cut point of
distillation of the distillation process is between 650 degrees
Fahrenheit (deg F.) and 1050 deg F. In certain aspects, the
intermediate unit is a thermal conversion process and the product
stream is a thermal liquid product. In certain aspects, the thermal
process can be selected from the group consisting of a coking
process and a visbreaking process. In certain aspects, the thermal
liquid product includes a concentration of the vacuum residue
fraction of less than 5 wt %. In certain aspects, the method
further includes the steps of pressurizing a crude oil stream in a
feed pump to a pressure at or greater than the critical pressure of
water to produce a pressurized oil, heating the pressurized oil in
a feed heater to a temperature at or less than 150 deg C. to
produce a hot oil stream, pressurizing the water stream in a water
pump to a pressure at or greater than the critical pressure of
water to produce a pressurized water, heating the pressurized water
in a water heater to a temperature at or greater than the critical
temperature of water to produce a supercritical water stream, and
mixing the hot oil stream and the supercritical water stream to
produce the mixed stream. In certain aspects, the method further
includes the steps of pressurizing a crude oil stream in a feed
pump to a pressure at or greater than the critical pressure of
water to produce a pressurized oil, pressurizing the water stream
in a water pump to a pressure at or greater than the critical
pressure of water to produce a pressurized water, mixing the
pressurized oil and pressurized water to produce the mixed stream,
a pressurized mix.
[0010] In a second aspect, an apparatus for upgrading a crude oil
stream is provided. The apparatus includes a pre-reaction stage
configured to produce a mixed stream from the crude oil stream and
a water stream, a reaction stage fluidly connected to the
pre-reaction stage. The reaction stage includes a convection
section of a furnace fluidly connected to the pre-reaction stage,
the convection section configured to subject the mixed stream to
conversion reactions to produce convection upgraded stream and a
supercritical reactor fluidly connected to the convection section,
the supercritical reactor configured to subject the convection
upgraded stream to conversion reactions to produce a reactor
effluent. The apparatus further includes a post-reaction stage
fluidly connected to the reaction stage, the post-reaction stage
configured to separate the reactor effluent to produce a
supercritical water (SCW)-treated product, wherein the SCW-treated
product includes an increased paraffin concentration as compared to
crude oil stream, wherein the SCW-treated product includes an
amount of water.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] These and other features, aspects, and advantages of the
scope will become better understood with regard to the following
descriptions, claims, and accompanying drawings. It is to be noted,
however, that the drawings illustrate only several embodiments and
are therefore not to be considered limiting of the scope as it can
admit to other equally effective embodiments.
[0012] FIG. 1 provides a process diagram of the process.
[0013] FIG. 2A provides a process diagram of an embodiment of an
integrated process.
[0014] FIG. 2B provides a process diagram of an embodiment of an
integrated process.
[0015] FIG. 3A provides a process diagram of an embodiment of an
integrated process.
[0016] FIG. 3B provides a process diagram of an embodiment of an
integrated process
[0017] FIG. 4 provides a process diagram of an embodiment of an
integrated process.
[0018] FIG. 5 provides a process diagram of an embodiment of an
integrated process.
[0019] FIG. 5A provides a process diagram of an embodiment of an
integrated process.
[0020] FIG. 6 provides a process diagram of an embodiment of an
integrated process.
[0021] FIG. 7 provides a process diagram of an embodiment of an
integrated process.
[0022] FIG. 8 provides a process diagram of an embodiment of an
integrated process.
[0023] In the accompanying Figures, similar components or features,
or both, may have a similar reference label.
DETAILED DESCRIPTION
[0024] While the scope of the apparatus and method will be
described with several embodiments, it is understood that one of
ordinary skill in the relevant art will appreciate that many
examples, variations and alterations to the apparatus and methods
described here are within the scope and spirit of the
embodiments.
[0025] Accordingly, the embodiments described are set forth without
any loss of generality, and without imposing limitations, on the
embodiments. Those of skill in the art understand that the scope
includes all possible combinations and uses of particular features
described in the specification.
[0026] Described here are processes and systems of an integrated
supercritical water and steam cracking process. The supercritical
water process can convert crude oil to a feedstock suitable for
stream cracking to produce light olefins, such as ethylene and
propylene, as well as aromatics such as benzene, toluene, and
xylene. The integrated supercritical water and steam cracking
process leads to synergy improving conversion to olefins.
[0027] The processes and systems of a supercritical water process
upstream of a steam cracking process advantageously overcomes
drawbacks of conventional pre-treating processes upstream of a
steam cracking process. The integrated supercritical water and
steam cracking process produces a greater liquid yield than a
conventional combination process. The processes and systems of an
integrated supercritical water and steam cracking process described
here can increase the hydrogen content of the feedstock to the
steam cracking process. An increased hydrogen content in the
feedstock can result in an increased yield of light olefins in the
product effluent from the steam cracking process.
[0028] The processes and systems of an integrated supercritical
water and steam cracking process described here can decrease the
amount of heavy residue fractions, such as atmospheric residue and
vacuum residue, in the product stream as compared to the feed
stream. Advantageously, decreasing the heavy residue fraction in
the feed to a steam cracker can reduce or mitigate coking; coke can
form a layer in the pyrolysis tube of the steam cracking process
which can inhibit heat transfer, cause physical failure of the
pyrolysis tube, and shorten the run length of a steam cracker
between cleaning and turnaround maintenance.
[0029] The processes and systems of an integrated supercritical
water and steam cracking process described here can decrease the
concentration of heteroatoms, such as sulfur compounds and metal
compounds in the product relative to the feed. Sulfur compounds can
suppress carbon monoxide formation in a steam cracking process by
passivating the inner surface of the pyrolysis tube. The presence
of sulfur can form nickel sulfide, passivating the nickel present
in the pyrolysis tube. Passivated nickel cannot catalyze coke
gasification, which produces carbon monoxide, so the passivation by
the presence of sulfur reduces the amount of carbon monoxide
produced. At pyrolysis conditions, passivation cannot be reversed,
that is at pyrolysis conditions the nickel does not return to
nickel metal or oxide by losing sulfur. In certain applications,
sulfur can be added to a feedstock for a steam cracking process to
maintain a sulfur concentration of between 20 parts-per-million by
weight (wt ppm) and 400 wt ppm. Sulfur concentrations greater than
400 wt ppm can increase the coking rate in a steam cracking
process.
[0030] Advantageously, the processes and systems of an integrated
supercritical water and steam cracking process described here can
expand the range of crude oils suitable for use to produce light
olefins.
[0031] As used throughout, "hydrogen content" refers to the
quantity of the hydrogen atoms bonded to carbon atoms and does not
refer to free hydrogen.
[0032] As used throughout, "external supply of hydrogen" refers to
the addition of hydrogen to the feed to the reactor or to the
reactor itself. For example, a reactor in the absence of an
external supply of hydrogen means that the feed to the reactor and
the reactor are in the absence of added hydrogen, gas (H.sub.2) or
liquid, such that no hydrogen (in the form H.sub.2) is a feed or a
part of a feed to the reactor.
[0033] As used throughout, "external supply of catalyst" refers to
the addition of catalyst to the feed to the reactor or the presence
of a catalyst in the reactor, such as a fixed bed catalyst in the
reactor. For example, a reactor in the absence of an external
supply of catalyst means no catalyst has been added to the feed to
the reactor and the reactor does not contain a catalyst bed in the
reactor.
[0034] As used throughout, "crude oil" refers to petroleum
hydrocarbon streams that can include whole range crude oil, reduced
crude oil, and refinery streams. "Whole range crude oil" refers to
passivated crude oil which has been processed by a gas-oil
separation plant after being recovered from a production well.
"Reduced crude oil" can also be known as "topped crude oil" and
refers to a crude oil having no light fraction, and would include
an atmospheric residue stream or a vacuum residue stream. Refinery
streams can include "cracked oil," such as light cycle oil, heavy
cycle oil, and streams from a fluid catalytic cracking unit (FCC),
such as slurry oil or decant oil, a heavy stream from hydrocracker
with a boiling point greater than 650 deg F., a deasphalted oil
(DAO) stream from a solvent extraction process, and a mixture of
atmospheric residue and hydrocracker bottom fractions.
[0035] As used throughout, "heavy oil" refers to hydrocarbons
heavier than gas oil and can include vacuum gas oil, atmospheric
residue, vacuum residue, and combinations of the same.
[0036] As used throughout, "atmospheric residue" or "atmospheric
residue fraction" refers to the fraction of oil-containing streams
having an initial boiling point (IBP) of 650 deg F., such that all
of the hydrocarbons have boiling points greater than 650 deg F. and
includes the vacuum residue fraction. Atmospheric residue can refer
to the composition of an entire stream, such as when the feedstock
is from an atmospheric distillation unit, or can refer to a
fraction of a stream, such as when a whole range crude is used.
[0037] As used throughout, "vacuum residue" or "vacuum residue
fraction" refers to the fraction of oil-containing streams having
an IBP of 1050 deg F. Vacuum residue can refer to the composition
of an entire stream, such as when the feedstock is from a vacuum
distillation unit or can refer to a fraction of stream, such as
when a whole range crude is used.
[0038] As used throughout, "asphaltene" refers to the fraction of
an oil-containing stream which is not soluble in a n-alkane,
particularly, n-heptane.
[0039] As used throughout, "heavy fraction" refers to the fraction
in the petroleum feed having a true boiling point (TBP) 10% that is
equal to or greater than 650 deg F. (343 deg C.), and alternately
equal to or greater than 1050 deg F. (566 deg C.). Examples of a
heavy fraction can include the atmospheric residue fraction or
vacuum residue fraction. The heavy fraction can include components
from the petroleum feed that were not converted in the
supercritical water reactor. The heavy fraction can also include
hydrocarbons that were dimerized or oligomerized in the
supercritical water reactor due to either lack of hydrogenation or
resistance to thermal cracking.
[0040] As used throughout, "light fraction" refers to the fraction
in the petroleum feed that is not considered the heavy fraction.
For example, when the heavy fraction refers to the fraction having
a TBP 10% that is equal to or greater than 650 deg F. the light
fraction has a TBP 90% that is less than 650 deg F. For example,
when the heavy fraction refers to the fraction having a TBP 10%
equal to or greater than 1050 deg F. the light fraction has a TBP
90% that is less than 1050 deg F.
[0041] As used throughout, "light olefins" refers to ethylene,
propylene, n-butene, iso-butene, 2-butenes and combinations of the
same. Each of ethylene, propylene, n-butene, and iso-butene is a
light olefin and together they are light olefins.
[0042] As used throughout, "long chain paraffins" refers to
paraffins with more than 4 carbons arranged in a line or chain.
[0043] As used throughout, "favor" means that reaction conditions
are disposed toward the production of certain products from the
reactant mixture.
[0044] As used throughout, "distillable fraction" or "distillate"
refers to the hydrocarbon fraction lighter than the distillation
residue from an atmospheric distillation process or a vacuum
distillation process.
[0045] As used here, "majority" means 51 percent (%) or more.
[0046] As used throughout, "coke" refers to the toluene insoluble
material present in petroleum.
[0047] As used throughout, "cracking" refers to the breaking of
hydrocarbons into smaller ones containing few carbon atoms due to
the breaking of carbon-carbon bonds.
[0048] As used throughout, "upgrade" means one or all of increasing
API gravity, decreasing the amount of impurities, such as sulfur,
nitrogen, and metals, decreasing the amount of asphaltene, and
increasing the amount of distillate in a process outlet stream
relative to the process feed stream. One of skill in the art
understands that upgrade can have a relative meaning such that a
stream can be upgraded in comparison to another stream, but can
still contain undesirable components such as impurities.
[0049] It is known in the art that hydrocarbon reactions in
supercritical water upgrade heavy oil and crude oil containing
sulfur compounds to produce products that have lighter fractions.
Supercritical water has unique properties making it suitable for
use as a petroleum reaction medium where the reaction objectives
can include upgrading reactions, desulfurization reactions
denitrogenation reactions, and demetallization reactions.
Supercritical water is water at a temperature at or greater than
the critical temperature of water and at a pressure at or greater
than the critical pressure of water. The critical temperature of
water is 373.946.degree. C. The critical pressure of water is 22.06
megapascals (MPa). Without being bound to a particular theory, it
is understood that the basic reaction mechanism of supercritical
water mediated petroleum processes is the same as a free radical
reaction mechanism. Thermal energy creates radicals through
chemical bond breakage. Supercritical water creates a "cage effect"
by surrounding the radicals. The radicals surrounded by water
molecules cannot react easily with each other, and thus,
intermolecular reactions that contribute to coke formation are
suppressed. The cage effect suppresses coke formation by limiting
inter-radical reactions compared to conventional thermal cracking
processes, such as delayed coker. Thermal cracking of a paraffin
feed can produce paraffins and olefins having reduced numbers of
carbons per molecule as compared to the paraffin feed. The relative
amount of paraffins and olefins and the distribution of carbon
numbers strongly depends on the phase where the thermal cracking
occurs. In the liquid phase, faster hydrogen transfer between
molecules occurs due to the high density creating closer distances
between the molecules which makes hydrogen transfer between
molecules easier and faster. Thus, the liquid phase facilitates the
formation of more paraffins than gas-phase cracking. Additionally,
liquid phase cracking shows generally even distribution of the
carbon numbers of the product while gas phase cracking has more
light paraffins and olefins in the product. While, supercritical
water facilitates hydrogen transfer between molecules, it is
inevitable to produce unsaturated hydrocarbons due to a limited
amount of available hydrogen. Unsaturated carbon-carbon bonds can
be distributed through the whole range of boiling points. Olefins,
as a representative unsaturated hydrocarbon, are valuable
chemicals, but low stability can cause many problems such as gum
formation when exposed to air. Thus, it is common practice in the
modern refinery to saturate olefins with hydrogen in the presence
of catalyst. Advantageously, at supercritical conditions water acts
as both a hydrogen source and a solvent (diluent) in upgrading
reactions, desulfurization reactions and demetallization reactions
and a catalyst is not needed. Hydrogen from the water molecules is
transferred to the hydrocarbons through direct transfer or through
indirect transfer, such as the water gas shift reaction.
[0050] As used here, "conversion reactions" refers to reactions
that can upgrade a hydrocarbon stream including cracking,
isomerization, alkylation, dimerization, aromatization,
cyclization, desulfurization, denitrogenation, deasphalting, and
demetallization.
[0051] As used here, "steam cracking process" refers to a process
where thermal cracking reactions occur in the presence of steam.
The steam cracking process can include a furnace. The furnace can
include a convection section and a radiation section. The
convection section can be used for preheating a feedstock stream, a
water stream, and other streams. The convection section can operate
at a temperature at or greater than 650 deg C. The convection
section can operate at a pressure between 2 bar (200 kPa) and 5 bar
(500 kPa). Steam can be injected with the hydrocarbon stream in the
convection section. Vaporization of the feed to a steam cracking
process can increase light olefin production. Vapor-phase cracking
of hydrocarbons in the convection section can lead to formation of
light molecules, such as C.sub.2 and C.sub.3 compounds, while
liquid-phase cracking can lead to middle range molecules, such as
C.sub.7 and C.sub.8 compounds. Operating conditions to increase
vaporization are maintained to avoid the conversion to coke due to
non-vaporized hydrocarbons. Steam, as a diluent, can suppress coke
formation. After passing through the convection section, the stream
can enter the radiation section where thermal cracking can occur.
The radiation section can operate at a temperature between 750 deg
C. and 850 deg C. The radiation section can operate at a pressure
between 2 bar and 5 bar. The radiation section can be used for
severe cracking of hydrocarbons to produce light olefins.
[0052] As used here, "supercritical water process" refers to a
process where crude oil undergoes conversion reactions in the
presence of supercritical water at supercritical conditions to
produce an upgraded hydrocarbon stream. A supercritical water
process includes a pre-reaction stage, a reaction stage, and a
post-reaction stage. The pre-reaction stage can include units to
pressurize, heat and mix the feed streams, such as pumps, heaters,
and mixers. The reaction stage can include at least one
supercritical water reactor. The post-reaction stage can include
units to separate the effluent from the reaction stage and can
include heat exchangers, pressure letdown devices, and one or more
separation vessels.
[0053] Referring to FIG. 1, a general process diagram of an
integrated supercritical water and steam cracking process is
provided. Stream A is produced in a supercritical water process
from a mixture of a crude oil and a water stream. The crude oil and
water stream can be pressurized or pressurized and heated in the
pre-reaction stage of the supercritical water process before
forming Stream A. Stream A is introduced to the convection section
of a furnace of a steam cracking process. The temperature of Stream
A is increased in the convection section to a temperature between
the critical temperature of water and 500 deg C. and alternately
between the critical temperature of water and 450 deg C. Conversion
reactions involving the components of Stream A begin to occur in
the convection section so as to produce a partially upgraded stream
in Stream B. Stream B can be introduced to the reaction stage of
the supercritical water process to be further upgraded. Stream C is
a product stream withdrawn from the post-reaction stage of the
supercritical water process and is upgraded relative to the crude
oil. The composition of Stream C, including the amount of water,
can be adjusted in the post-reaction stage of the supercritical
water process. Stream C can be combined with a diluent steam and
introduced to the convection section of the furnace. The need for
diluent steam can be determined based on a composition of Stream C.
In the convection section, components of Stream C can mix with
components of Stream A and can be carried out in Stream B.
Components of Stream C can enter the radiation section of the
furnace and be carried out in Stream D. Stream D can contain
olefins and other cracked hydrocarbon components.
[0054] The following embodiments, provided with reference to the
figures, describe the integrated supercritical water and steam
cracking process in more detail
[0055] An integrated supercritical water and steam cracking process
is described with reference to FIG. 2A.
[0056] In pre-reaction stage 100, crude oil stream 2 can include
crude oil. In at least one embodiment, crude oil stream 2 can
include an atmospheric residue fraction of between 20 wt % and 95
wt % and a vacuum residue fraction of between 3 wt % and 50 wt %.
Crude oil stream 2 can be pressurized in feed pump 115 to a
pressure greater than the critical pressure of water to produce
pressurized oil 215. Pressurized oil 215 can be heated in feed
heater 120 to produce hot oil stream 220. Feed heater 120 can be
any type of heater capable of increasing the temperature of
pressurized oil 215 such as a gas fired heater or an electric
heater. The temperature of hot oil stream 220 can be less than the
critical temperature of water, alternately equal to about 150 deg
C., and alternately less than 150 deg C. Maintaining the
temperature of hot oil stream 220 at less than the critical
temperature of water reduces the formation of coke in hot oil
stream 220 and in supercritical reactor 140.
[0057] Water stream 4 can be a demineralized water having a
conductivity less than 1.0 microSiemens per centimeter (.mu.S/cm),
and alternately less than 0.1 .mu.S/cm. In at least one embodiment,
water stream 4 is demineralized water having a conductivity less
than 0.1 .mu.S/cm. Water stream 4 can be pressurized in water pump
105 to a pressure greater than the critical pressure of water to
produce pressurized water 205. Pressurized water 205 can be heated
in water heater 110 to produce supercritical water stream 210. The
temperature of supercritical water stream 210 can be equal to or
greater than the critical temperature of water, alternately equal
to or greater than 380 deg C., and alternately between 380 deg C.
and 500 deg C.
[0058] Feed pump 115 and water pump 105 can be any pumps capable of
increasing the pressure of the respective fluid stream to a
pressure greater than the critical pressure of water. In at least
one embodiment, feed pump 115 and water pump 105 can be diaphragm
metering pumps.
[0059] Feed heater 120 and water heater 110 can be any type of
exchangers capable of increasing the temperature of the respective
fluid stream. In at least one embodiment, feed heater 120 can be a
cross exchanger removing heat from another portion of the process
to increase the temperature of pressurized oil 215. In at least one
embodiment, water heater 110 can be a cross exchanger removing heat
from another portion of the process to increase the temperature of
pressurized water 205. In some embodiments, feed heater 120 and
water heater 110 can be fluidly connected on the heat transfer
medium side. That is the heat transfer medium used to heat feed
heater 120 and water heater 110 can be from the same source.
[0060] Hot oil stream 220 and supercritical water stream 210 can be
mixed in mixer 130 to produce mixed stream 230. The ratio of the
volumetric flow rate of hot oil stream 220 to supercritical water
stream 210 can be between 1:10 and 10:1 at standard temperature and
pressure (SATP), and alternately between 1:5 and 5:1 at SATP. Mixer
130 can be any mixing device suitable for mixing a hydrocarbon
stream with a water stream. Examples of mixer 130 can include an
ultrasonic device and a tee fitting. Mixed stream 230 can be at a
pressure at or greater than the critical pressure of water. Mixed
stream 230 can be at a temperature in the range from between 200
deg C. to 500 deg C., alternately between 200 deg C. to 450 deg C.,
alternately in the range from between 320 deg C. and 450 deg C. The
temperature of mixed stream 230 can depend on the temperatures of
supercritical water stream 210 and hot oil stream 220.
[0061] In at least one embodiment of the integrated supercritical
water and steam cracking process, mixed stream 230 can be
introduced to furnace 310. In at least one embodiment, the entire
volume of mixed stream 230 is introduced to convection section 312
of furnace 310. In at least one embodiment, a portion of mixed
stream 230 is introduced to convection section 312 of furnace
310.
[0062] Reaction stage 190 includes convection section 312 of
furnace 310 and supercritical reactor 140. Mixed stream 230 can be
introduced to convection section 312 of furnace 310 and can be
heated in convection section 312 by hot flue gas from radiation
section 314 to produce convection upgraded stream 25. Convection
section 312 can be designed to achieve a Reynolds number of at
least 4000 of the streams in convection section 312. A Reynolds
number of at least 4000 can ensure development of full turbulence.
Full turbulence can increase mixing between the hydrocarbons and
the supercritical water in mixed stream 230. Mixed stream 230 can
undergo conversion reactions in convection section 312, such that
hydrocarbons in mixed stream 230 undergo conversion reactions in
the presence of supercritical water from mixed stream 230.
Convection upgraded stream 25 can be at a temperature between the
critical temperature of water and 650 deg C., alternately between
the critical temperature of water and 500 deg C., alternately
between the critical temperature of water and 450 deg C., and
alternately between the critical temperature of water and 420 deg
C. The pressure of convection section 312 can be between 2 bar (200
kPa) and 5 bar (500 kPa). The residence time of mixed stream 230 in
convection section 312 can be less than 60 minutes, and alternately
less than 30 minutes. The residence time of mixed stream 230 can be
adjusted to limit the temperature of convection upgraded stream 25.
The flow path of mixed stream 230 in convection section 312 can be
in a downward path, and alternately can be in a horizontal path. In
at least one embodiment, the flow path of mixed stream 230 is in
the absence of an upflow path.
[0063] Advantageously, the presence of supercritical water in mixed
stream 230 can suppress coke formation and formation of gas
compounds compared to processes that use the convection section of
a steam cracking furnace to preheat a feedstock or to thermal crack
a feedstock in the absence of supercritical water. Examples of gas
compounds can include methane, ethane, ethylene, propane,
propylene, butanes, butenes, and combinations thereof.
[0064] In at least one embodiment, convection upgraded stream 25
can be introduced to supercritical reactor 140 to produce reactor
effluent 240. The reaction conditions in supercritical reactor 140
can be maintained such that conversion reactions occur. The
conversion reactions that occur in supercritical reactor 140 can be
the same reactions that occur in convection section 312. Reaction
conditions can include the temperature, pressure, and residence
time. The temperature of supercritical reactor 140 can be greater
than the critical temperature of water, alternately between 380 deg
C. and 480 deg C., and alternately between 390 deg C. and 450 deg
C. The pressure in supercritical reactor 140 can be greater than
the critical pressure of water, alternately between 23 MPa and 35
MPa, and alternately between 24 MPa and 30 MPa. Pressure in
supercritical reactor 140 can be controlled by depressurizing
device 160. Supercritical reactor 140 can be a tubular type
reactor. The residence time of supercritical reactor 140 can be
between 10 seconds and 120 minutes, and alternately between 5
minutes and 30 minutes. In at least one embodiment, the residence
time of supercritical reactor 140 is between 5 minutes and 30
minutes. Supercritical reactor 140 can be in the absence of an
external supply of hydrogen. Supercritical reactor 140 can be in
the absence of an external supply of catalyst.
[0065] Reactor effluent 240 can be introduced to post-reaction
stage 200 to produce SCW-treated product 10.
[0066] Reactor effluent 240 is introduced to cooling device 150 to
reduce the temperature of reactor effluent 240 to produce cooled
effluent 250. Cooling device 150 can be one heat exchanger or a
series of heat exchangers. In at least one embodiment, cooling
device 150 includes a heat exchanger that can be used to heat
pressurized water 205 by cross exchange with reactor effluent 240.
In at least one embodiment, cooling device 150 can include one or
more heat exchangers capable of removing heat from reactor effluent
240 to produce steam. Cooling device 150 can include any type of
heat exchanger capable of decreasing the temperature of reactor
effluent 240. In at least one embodiment, cooling device 150 can be
a cross exchanger capable of removing heat from reactor effluent
240 to heat another stream.
[0067] Cooled effluent 250 can be depressurized in depressurizing
device 160 to produce depressurized effluent 260. Depressurizing
device 160 can be any device capable of reducing the pressure of
cooled effluent 250. In at least one embodiment, depressurizing
device 160 can be a back pressure regulator. In at least one
embodiment, depressurizing device 160 can be a pressure control
valve.
[0068] Depressurized effluent 260 is introduced to gas-liquid
separator 170 to produce gas stream 270 and liquid stream 275. Gas
stream 270 can contain hydrogen, hydrogen sulfide, methane, ethane,
propane, ethylene, carbon monoxide, carbon dioxide, and
combinations of the same. Liquid stream 275 is introduced to
oil-water separator 180 to produce SCW-treated product 10 and
produced water 285.
[0069] Produced water 285 can contain an amount of hydrocarbons.
The amount of hydrocarbons in produced water 285 can be measured as
total organic carbon (TOC). Hydrocarbons in produced water 285
means a loss of oil from SCW-treated product 10, therefore the TOC
of produced water 285 can be less than 5 grams of organic carbon in
100 grams of water (0.5 wt %), alternately less than 0.1 wt %, and
alternately less than 0.02 wt %. In at least one embodiment, the
TOC in produced water 285 is less than 0.02 wt %.
[0070] The operating conditions of depressurizing device 160,
gas-liquid separator 170, and oil-water separator 180 can be
adjusted to control an amount of water in SCW-treated product 10.
In at least one embodiment, the residence times in gas-liquid
separator 170 and oil-water separator 180 can control the amount of
water in SCW-treated product 10. In at least one embodiment,
shorter residence times in gas-liquid separator 170 and oil-water
separator 180 can increase the amount of water in SCW-treated
product 10. In at least one embodiment, adding a demulsifier to
liquid stream 275 can enhance the separation in oil-water separator
180 and can control the amount of water in SCW-treated product 10.
In at least one embodiment, demulsifier can be added to liquid
stream 275 in the range from 0.01 wt % to 0.1 wt % (weight of
demulsifier to weight of liquid stream 275). In at least one
embodiment, SCW-treated product 10 can contain an amount of water.
The amount of water in SCW-treated product 10 can be less than 1
percent by weight (wt %) water, alternately less than 0.1 wt % of
water (1,000 wt ppm), alternately less than 0.05 wt % (500 wt ppm),
alternately less than 0.01 wt % (100 wt ppm), alternately between
0.03 wt % (300 ppm) and 0.1 wt % of water, and alternately between
0.03 wt % (300 ppm) and 1 wt % of water.
[0071] SCW-treated product 10 contains an upgraded oil. SCW-treated
product 10 can include a distillable fraction, an atmospheric
residue fraction, and a vacuum residue fraction. SCW-treated
product 10 can have a paraffin concentration. SCW-treated product
10 can have an increased paraffin concentration by weight in the
distillable fraction as compared to crude oil stream 2. In at least
one embodiment, SCW-treated product 10 can have a reduced
concentration of an atmospheric residue fraction as compared to the
concentration of the atmospheric residue fraction in crude oil
stream 2. In at least one embodiment, SCW-treated product 10 can
have a reduced concentration of a vacuum residue fraction as
compared to the concentration of the vacuum residue fraction in
crude oil stream 2. In at least one embodiment, SCW-treated product
10 can include n-paraffins and .alpha.-olefins in the distillable
fraction due to the cracking of alkyl-substituted aromatic
compounds in convection section 312 and supercritical water reactor
140, where the alkyl-substituted aromatic compounds have alkyl
groups with long chain paraffins attached to the aromatic cores. In
at least one embodiment, SCW-treated product 10 has a decreased
concentration of heteroatoms, such as sulfur compounds, nitrogen
compounds, and metal compounds as compared to crude oil stream
2.
[0072] SCW-treated product 10 can be introduced to convection
section 312 of furnace 310. The components of SCW-treated product
10 can mix with the diluent components from mixed stream 230 after
it enters convection section 312. Components of SCW-treated product
10 can mix with the diluent components in radiation section 314 to
produce furnace effluent 20. Furnace effluent 20 can include
olefins.
[0073] The reactions in furnace 310 can include radical-mediated
reactions that occur in the radiation section of furnace 310. At
temperatures between 750 deg C. and 875 deg C., hydrocarbon
molecules can be cracked to generate a radical. Through propagation
of radicals, new molecules and radicals can be generated. In steam
cracking, the low operating pressure and presence of steam as a
diluent favor the production of light olefins.
[0074] Advantageously, SCW-treated product 10 is a water-in-oil
emulsion, with the amount of water controlled by separation.
Advantageously, the presence of emulsified water in SCW-treated
product 10 can assist vaporization of hydrocarbons in furnace 310
because the emulsified water has a boiling point greater than 100
deg C. A boiling point greater than 100 deg C. of the emulsified
water can be due to the pressure in furnace 310, the emulsified
state of the water or both. The emulsified water stays in emulsion
for longer resulting in thermal cracking of the hydrocarbons and
suppression of coke formation.
[0075] Referring to FIG. 2B with reference to FIG. 2A, an alternate
embodiment of the integrated supercritical water and steam cracking
process is provided. Pressurized oil 215 and pressurized water 205
can be mixed in mixer 130 to produced pressurized mix 235, a mixed
stream. Pressurized mix 235 can be introduced to convection section
312 to produce convection upgraded stream 25.
[0076] Referring to FIG. 3A with reference to FIG. 2A, a process
flow diagram of a steam cracking process 300 is provided. Furnace
310 is a unit of steam cracking process 300. Furnace 310 produces
furnace effluent 20, which can be introduced to cracker downstream
unit 320. Furnace effluent 20 can contain a greater amount of light
olefins, methane, acetylene, benzene, toluene, xylene, pyrolysis
gasoline, pyrolysis fuel oil and other products as compared to
crude oil stream 2. Other products can include coke.
[0077] Cracker downstream unit 320 can include operational units to
further process furnace effluent 20, including further cracking
units, heat recovery units, depressurization units, and separation
units. Cracker downstream unit 320 can produce cracked product 30
and fuel oil 32. Cracked product 30 can include light olefins,
methane, and ethane. Cracked product 30 has a greater amount of
light olefins as compared to a product from a steam cracking
process in the absence of being integrated with a supercritical
water process. Fuel oil 32 can include pyrolysis fuel oil with a
boiling point greater than 200 deg C., which can be an unstable and
low quality hydrocarbon stream that is useful as a fuel oil. Fuel
oil 32 can have a yield that is less than 30 wt % of the feed to
steam cracking process 300. In at least one embodiment, fuel oil 32
can have a yield that is less than 30 wt % of SCW-treated product
10.
[0078] In at least one embodiment, as shown in FIG. 3B, gas stream
270 can be introduced to sweetening process 350 to remove hydrogen
sulfide from the stream to produced sweetened gas stream 370.
Sweetening process 350 can be any type of unit capable of
sweetening a gas phase stream by removing sulfur compounds.
Examples of sweetening units can include the use of an alkaline
solution. Sweetened gas stream 370 can be transferred to steam
cracking process 300 as a feed or a fuel gas. Advantageously,
sweetening process 350 enables use of the by-product gases from the
supercritical water process for steam cracking. Sulfur compounds
can reduce coke formation in steam cracker through passivation of
the inner wall of the cracking coil. However, sulfur compounds also
cause severe corrosion in the steam cracking zone as well as in
downstream units, such as quenching process. Therefore, sweetening
process 350 enables use of gas stream 270 in steam cracking process
300.
[0079] The composition of the crude oil stream can impact the
composition of the SCW-treated product. The composition of the
SCW-treated product can impact whether the SCW-product is suitable
for treatment in the steam cracking process. In embodiments, where
the composition of the SCW-treated product is not suitable for
treatment in the steam cracking process, the SCW-treated product
can be introduced to an intermediate unit to produce a product
stream and the product stream can be introduced to the steam
cracking process. The composition of the SCW-treated product is
suitable for treatment in the steam cracking process when the
concentration of the vacuum residue fraction in the SCW-treated
product is less than 5 wt % and alternately less than 3 wt %. The
concentration of the vacuum residue fraction can be measured using
simulated distillation (SIMDIS), a common method described in ASTM
D 7169. When the concentration of the vacuum residue fraction is
greater than 5 wt %, severe coking can occur in a steam cracking
process which can cause pressure drop throughout the steam cracking
tubes and can inhibit heat transfer between the heat source, such
as a flame, and the fluid in the steam cracking tubes. A buildup of
coke on the steam cracking tubes can act as an insulator which
disrupts the heat transfer process.
[0080] The combination of convection section 312 and supercritical
reactor 140 can convert 80 wt % of the vacuum residue fraction in
crude oil stream 2 to light fraction components, alternately 75 wt
% of the vacuum residue fraction in crude oil stream 2 to light
fraction components, and alternately at least 70 wt % of the vacuum
residue fraction in crude oil stream 2 to light fraction
components. In at least one embodiment, crude oil stream 2 contains
a concentration of vacuum residue fraction of less than 20 wt % and
the combination of convection section 312 and supercritical reactor
140 converts 75 wt % of the vacuum residue fraction in crude oil
stream 2 to light fraction components resulting in SCW-treated
product 10 containing less than 5 wt % vacuum residue fraction.
[0081] In embodiments where the composition of the SCW-treated
product contains a concentration of the vacuum residue fraction of
greater than 5 wt %, an intermediate unit can process the
SCW-treated product to produce a product stream suitable for use in
the steam cracking process. Examples of the intermediate unit can
include a hydrotreating process, a distillation process, and a
thermal conversion process. Advantageously, the intermediate unit
can remove a portion of the vacuum residue fraction present in the
SCW-treated product.
[0082] Referring to FIG. 4, with reference to FIG. 2A, an
embodiment of an integrated supercritical water and steam cracking
process with an intermediate unit is provided. SCW-treated product
10 is introduced to hydrotreating process 400. Hydrotreating
process 400 can treat SCW-treated product 10 to produce
hydrotreating process (HTP)-product 40. Hydrotreating process 400
advantageously can be used to process SCW-treated product 10 when
the concentration of the vacuum residue fraction of crude oil
stream 2 is greater than 20 wt % and the total sulfur content of
crude oil stream 2 is greater than 1.5 wt % of sulfur. In at least
one embodiment, the concentration of water in SCW-treated product
10 is less than 1,000 wt ppm, and alternately less than 100 wt ppm
prior to being introduced to hydrotreating process 400.
Advantageously, a concentration of water in SCW-treated product 10
of less than 1,000 wt ppm can limit deactivation of a hydrotreating
catalyst by water.
[0083] Hydrogen gas stream 6 is introduced to hydrotreating process
400. Hydrogen gas stream 6 can be from any source of hydrogen gas.
In at least one embodiment, hydrogen gas stream 6 can be recycled
from steam cracking process 300, where hydrogen gas can be
generated. The ratio of the flow rate of hydrogen gas stream 6 to
the flow rate of SCW-treated product 10 can be between 100 cubic
nanometers per kiloliter (nm.sup.3/kL) and 800 nm.sup.3/kL, and
alternately between 200 nm.sup.3/kL and 500 nm.sup.3/kL.
[0084] Hydrotreating process 400 can contain a hydrotreating
catalyst. The hydrotreating catalyst can be a cobalt-molybdenum
(CoMo), nickel-molybdenum (NiMo), or any other catalyst known in
the art. In hydrotreating process 400, hydrotreating reactions can
occur such as hydrogenation, hydrodesulfurization, and
hydronitrogenation. Hydrogenation reactions can hydrogenate
unsaturated bonds, including of olefins. Hydrodesulfurization and
hydronitrogenation reactions with hydrotreating catalyst can remove
sulfur from compounds upgraded by the supercritical water process.
The supercritical water process can convert large sulfur molecules
into lighter sulfur molecules such as alkyl thiophenes and thiols.
Lighter sulfur molecules can exhibit increased reactivity of sulfur
compounds, such that sulfur can be removed more easily from lighter
sulfur molecules.
[0085] Hydrotreating process 400 can include a hydrotreating
reactor. The operating temperature of the hydrotreating reactor can
be between 300 deg C. and 480 deg C. and alternately between 320
deg C. and 400 deg C. In the hydrotreating reactor, in the presence
of the hydrotreating catalyst, unsaturated bonds of the
hydrocarbons present in SCW-treated product 10 can be hydrogenated
by hydrotreating. The olefin saturation reaction is exothermic and
the operating temperature should be kept as low as possible. The
operating pressure of the hydrotreating reactor can be between 3
MPa and 25 MPa, and alternately between 5 MPa and 15 MPa. The
liquid hourly space velocity of the hydrotreating reactor can be
between 0.1 per hour (/hr) and 2/hr, and alternately between 0.2/hr
and 1/hr.
[0086] HTP-treated product 40 can be introduced to the furnace of
steam cracking process 300. HTP-treated product 40 can be used a
feedstock to the furnace for steam cracking. HTP-treated product 40
can have a boiling point range that is less than the boiling point
range of SCW-treated product 10 due to hydrogenative and catalytic
upgrading in hydrotreating process 400. The amount of heavy
fractions in HTP-treated product 40 is less than the amount in
SCW-treated product 10. The amount of impurities such as sulfur,
nitrogen and metals in HTP-treated product 40 is less than the
amount in SCW-treated product 10. The operating conditions, such as
temperature and pressure, of HTP-treated product 40 can be adjusted
based on the operating conditions of steam cracking process 300. In
at least one embodiment, the temperature of HTP-treated product 40
can be in the range from about 10 deg C. to about 400 deg C. when
entering steam cracking process 300. In at least one embodiment,
the pressure of HTP-treated product 40 can be in the range from
about 0.01 MPa to about 5 MPa when entering steam cracking process
300. In at least one embodiment, HTP-treated product 40 is reduce
to a temperature between 30 deg C. and 90 deg C. and reduced to a
pressure of ambient pressure. In at least one embodiment, a diluent
stream is mixed with HTP-treated product 40 prior to being
introduced to the furnace of steam cracking process 300. The
diluent stream can be steam. Hydrotreating process 400 can include
heat exchangers, depressurizing valves, and other process units
that can adjust operating conditions downstream of the
hydrotreating reactor.
[0087] Advantageously, the integrated supercritical water and steam
cracking process can remove metallic compounds from crude oil
stream 2, where the metallic compounds can be separated from the
upgraded oil into the water. As result, SCW-treated product 10
contains a reduced metallic content as compared to crude oil stream
2. The reduced metallic content of SCW-treated product 10 results
in a longer life for the hydrotreating catalyst in hydrotreating
process 400 as compared to a conventional hydrotreating process
treating crude oil.
[0088] Advantageously, the integrated supercritical water and steam
cracking process can convert asphaltene to maltene without
generating coke. Therefore, SCW-treated product 10 can have a
reduced asphaltene concentration as compared to crude oil stream 2.
Asphaltene is a known precursor for coke formation on a
hydrotreating catalyst. Therefore, the reduced asphaltene results
in a longer life for the hydrotreating catalyst in hydrotreating
process 400 as compared to a conventional hydrotreating process
treating crude oil.
[0089] Advantageously, treatment of crude oil by the integrated
supercritical water and steam cracking process can relieve load to
hydrotreating process 400 thus allowing for milder conditions in
hydrotreating process 400 than would otherwise be expected in a
hydrotreating process. As used here, "relieve load" means a reduced
operating pressure in hydrotreating process, a reduced operating
temperature in hydrotreating process, a shorter residence time in
hydrotreating process, a longer catalyst life time in hydrotreating
process, less production of light gases, such as methane and ethane
in hydrotreating process, and reduced operating cost in
hydrotreating process.
[0090] In at least one embodiment, fuel oil 32 can have a yield
that is less than 30 wt % of HTP-treated product 40.
[0091] Referring to FIG. 5, with reference to FIG. 2A, an
embodiment of an integrated supercritical water and steam cracking
process with an intermediate unit is provided. SCW-treated product
10 is introduced to distillation process 500. Distillation process
500 can be any distillation process capable of separating streams.
Examples of distillation process 500 include an atmospheric
distillation unit, vacuum distillation unit, or a combination
thereof. In at least one embodiment, distillation process 500 can
include a distillation unit. Distillation process 500 can distill
SCW-treated product 10 to produce distilled product 50 and
distilled residue 55. Distilled product 50 can be introduced to the
furnace of steam cracking process 300.
[0092] Distillation process 500 advantageously can be used to
process SCW-treated product 10 when the concentration of the vacuum
residue fraction of crude oil stream 2 is greater than 20 wt % or
the concentration of the vacuum residue fraction of SCW-treated
product 10 is greater than 5 wt %. Distillation process 500 can use
steam as an energy carrier and diluent in the distillation unit. In
at least one embodiment, the concentration of water in SCW-treated
product 10 can be less than 1 pound per barrel (lb/barrel). In at
least one embodiment, the concentration of water in SCW-treated
product 10 can be less than 0.3 wt %.
[0093] The cut point of distillation of distillation process 500
can be selected based on the specifications of steam cracking
process 300. As used here, "cut point" refers to the final boiling
point of distillates. The cut point of distillation of distillation
process 500 can be between 650 deg F. and 1050 deg F., alternately
between 850 deg F. and 1050 deg F. In at least one embodiment, the
cut point of distillation of distillation process 500 can be
designed to remove or eliminate the vacuum residue fraction from
distilled product 50. In at least one embodiment, the cut point of
distillation process 500 is between 850 deg F. and 1050 deg F. The
greater the cut point of distillation, the greater the volume of
distilled product 50 that can be directed toward steam cracking
process 300; however, coke formation can be increased due to a
shorter run length. Increased coke formation can lead to a
requirement for decoking. The cut point of distillation can be
determined in consideration of steam cracking process 300 and
available decoking processes.
[0094] Distilled residue 55 can contain the fraction separated by
the cut point. In at least one embodiment, distilled residue 55 can
be recycled to the front end of the integrated supercritical water
and steam cracking process and can be mixed with crude oil 2. In at
least one embodiment, distilled residue 55 can be combined with
fuel oil 32. In at least one embodiment, fuel oil 32 can have a
yield that is less than 30 wt % of distilled product 50.
[0095] Referring to FIG. 5A, with reference to FIG. 2A, an
embodiment of an integrated supercritical water and steam cracking
process with distillation process 500 is provided. Depressurized
effluent 260 can be introduced to convection section 312.
Depressurized effluent 260 can be at a pressure between 1 pounds
per square inch (psig) and 200 psig. Depressurized effluent 260 can
be at a temperature of less than the critical temperature of water.
Cooling of depressurized effluent 260 can be due to pressure
letdown without additional temperature reducing device.
Depressurized effluent 260 is an emulsion and can be heated by
passing through convection section 312 to produce heated emulsion
34. Heated emulsion 34 can be at the same pressure as depressurized
effluent 260. Heated emulsion 34 can be at a temperature between
350 deg C. and 600 deg C. The temperature of heated emulsion 34 can
be adjusted based on the cut point of distillation in distillation
process 500. Heated emulsion 34 can be introduced to distillation
process 500 to produce distilled product 50 and distilled residue
55.
[0096] Distilled residue 55 can contain dirty water. The dirty
water can include water and metal compounds.
[0097] Distilled product 50 can contain the majority of water
present in heated emulsion 34. Distilled product 50 can be
introduced to convection section 312 of furnace 310. Diluent stream
36 can be mixed with distilled product 50 before being added to
convection section 312. Diluent stream 36 can include water at a
temperature and pressure such that the water is present in diluent
stream 36 as steam. The steam to oil ratio for furnace 310 can be
between 0.4 kilogram-steam per kilogram-oil (kg-steam/kg-oil) and
1.0 kg-steam/kg-oil. In general the heavier the feed, the greater
the volume of steam to be included in furnace 310. In at least one
embodiment, the water concentration in distilled product 50 can be
measured and the volume of diluent stream 36 can be adjusted based
on the measured amount of water in distilled product 50.
Advantageously, introducing depressurized effluent 260 to
convection section 312 and using distillation process 500 to
separate distilled product 50, can reduce the amount of diluent
stream 36 used in convection section 312.
[0098] Referring to FIG. 6, an embodiment of an integrated
supercritical water and steam cracking process with an intermediate
unit is provided. SCW-treated product 10 is introduced to thermal
conversion process 600. Thermal conversion process 600 can include
a coking process and a visbreaking process. Coking processes can
include a delayed coker process and a fluid coker process. A
visbreaking process can operate at a temperature between 450 deg C.
and 500 deg C., a pressure between 1 MPa and 2.5 MPa, and a
residence time between 1 minute and 20 minutes. A delayed coker
process can operate at a temperature between 410 deg C. and 470 deg
C., a pressure between 0.04 MPa and 0.17 MPa, and a residence time
between 5 hours and 20 hours. A fluid coker process can operate at
a temperature between 480 deg C. and 560 deg C., a pressure at
ambient pressure, and a residence time between 5 seconds and 20
seconds.
[0099] Thermal conversion process 600 converts the upgraded oil in
SCW-treated product 10 to produce thermal liquid product 60, coke
62, and thermal gas product 64. In at least one embodiment, thermal
conversion process 600 can be a delayed coker. Thermal liquid
product 60 contains less than 5 wt % vacuum residue fraction. Coke
62 can contain solid coke, pitch, heavy molecules such as
asphaltenes, and combinations of the same. Thermal gas product 64
can include methane, ethane, ethylene, propane, propylene, hydrogen
sulfide, other light molecules, and combinations of the same.
Thermal liquid product 60 can be introduced to steam cracking
process 300.
[0100] Thermal conversion process 600 advantageously can be used to
process SCW-treated product 10 when the vacuum residue fraction of
crude oil stream 2 is greater than 20 wt % or the vacuum residue
fraction of SCW-treated product 10 is greater than 5 wt %. In at
least one embodiment, the concentration of water in SCW-treated
product 10 can be less than 20 wt % prior to entering thermal
conversion process 600. The amount of water in SCW-treated product
10 can be adjusted based on the process design of thermal
conversion process 600, the energy demands, and the desired product
composition. The amount of water in SCW-treated product 10 can
reduce coke generation, by generating hydrogen through reforming
and due to the water-gas shift reaction. The amount of water in
SCW-treated product 10 can increase liquid product yield in thermal
conversion process 600.
[0101] In certain embodiments, when thermal liquid product 60
contains a concentration of vacuum residue fraction of greater than
5 wt %, thermal liquid product 60 can be processed in another unit
such as a distillation or fractionation unit to remove the vacuum
residue fraction and therefore reduce the concentration of vacuum
residue fraction to less than 5 wt % prior to being introduced to
steam cracking process 300.
[0102] Thermal gas product 64 can be introduced to steam cracking
process 300 (not shown) as a feed or as a fuel.
[0103] While the embodiments here have been described with
reference to the integrated supercritical water and steam cracking
process described with reference to FIG. 2A, it is understood that
the embodiments of a supercritical water and steam cracking process
with an intermediate unit could also be employed with reference to
the integrated supercritical water and steam cracking process
described with reference to FIG. 2B.
[0104] Embodiments of an integrated supercritical water and steam
cracking process are in the absence of a delayed coker. A delayed
coker can produce large amounts of solid coke which is problematic
for a steam cracking process. In addition, a delayed coker can
produce a large amount of gases such as methane and ethane, which
can include hydrogen. A supercritical water process can produce
less gas than a delayed coker thus keeping more hydrogen in the
liquid hydrocarbon product. This means that the liquid product from
a delayed coker has a lesser hydrogen to carbon ratio than a liquid
product from a supercritical water process. In addition, a
supercritical water process can produce less coke than a delayed
coker.
EXAMPLES
Example 1
[0105] Example 1 contains Aspen HYSYS.RTM. simulations from Aspen
Technology, Inc. Bedford, Mass. illustrating the integration of the
convection section of the furnace to the supercritical water
process. In a first simulation, with reference to FIG. 7 and FIG.
2A, water stream 4 was simulated as a demineralized water with a
conductivity of less than 0.1 .mu.S/cm. The composition of crude
oil stream 2 is shown in Table 1. Pressurized water 205 is
pre-heated by cross-exchange with cooling device 150 to produce
pre-heated water 705. Pre-heated water 705 is heated in water
heater 110 to produce supercritical water stream 210.
[0106] Mixed stream 230 is introduced to supercritical reactor 140.
Reactions occur in supercritical reactor 140 with a residence time
of less than 15 minutes.
[0107] Supercritical reactor 140 was simulated as a tubular-type
reactor to give residence time to the mixed stream of at least 15
minute. Depressurized effluent 260 is introduced to gas-liquid
separator 170, which produced vapor stream 770 and liquid stream
275. Vapor stream 770 is introduced to vapor separator 700, which
produced gas stream 270 and separated liquid 775. Liquid stream 275
and separated liquid 775 are introduced to oil-water separator 180
to produce SCW-treated product 10 and produced water 285.
[0108] The properties of SCW-treated product 10 are in Table 1.
Operating conditions of the streams are in Table 2.
[0109] Table 1 provides the properties of the streams.
TABLE-US-00001 TABLE 1 Stream properties for Example 1. Properties
Stream 2 Stream 10 Specific Gravity (API) 28.2 34.2 TBP 5% (deg C.)
41 35 TBP 10% (deg C.) 92 98 TBP 30% (deg C.) 234 215 TBP 50% (deg
C.) 363 337 TBP 70% (deg C.) 524 453 TBP 90% (deg C.) 745 596 TBP
95% (deg C.) 819 634 Sulfur Content (wt %) 2.9 2.7 Nitrogen Content
(wt ppm) 1536 925 Kinematic Viscosity at 16.7 1.5 100 deg F.
(centistokes (cSt))
TABLE-US-00002 TABLE 2 Operating Conditions of the Simulation
according to FIG. 7 Mass Flow (kilograms Liquid Temperature
Pressure per hour Volume Flow Stream (deg C.) (psig) (kg/h))
(barrel/day) Stream 4 20 1 661.1 100.00 Stream 205 22 3901 661.1
100.00 Stream 705 337 3901 661.1 100.00 Stream 210 400 3901 661.1
100.00 Stream 2 20 1 600.0 100.00 Stream 215 21 3901 600.0 100.00
Stream 220 150 3901 600.0 100.00 Stream 230 368 3901 1261.1 200.00
Stream 240 450 3901 1261.1 206.3 Stream 250 150 3901 1261.1 206.3
Stream 260 153 100 120.0 206.3 Stream 270 50 1 0.6 0.1 Stream 285
50 1 661.0 100.0 Stream 10 50 1 599.5 106.2
[0110] In a second simulation, with reference to FIG. 2A, FIG. 7,
and FIG. 8, pre-heated water 705 is introduced to convection
section 312 of furnace 310 to produce heated water 805. Therefore,
the embodiment of the process as shown in FIG. 8 is in the absence
of water heater 110. Heated water 805 is mixed with hot oil 220 in
mixer 130 to produce mixed feed 815. Mixed feed 815 can have the
same operating conditions as described with reference to mixed
stream 230. Mixed feed 815 is introduced to convection section 312
of furnace 310 where the hydrocarbons present in mixed feed 815
undergo conversion reactions in the presence of supercritical water
in convection section 312. Convection section 312 is simulated to
provide a Reynolds number of 4000 in convection section 312. Table
3 contains those streams that are not already disclosed in Table
2.
TABLE-US-00003 TABLE 3 Operating Conditions of the Simulation
according to FIG. 8 Mass Flow (kilograms Liquid Temperature
Pressure per hour Volume Flow Stream (deg C.) (psig) (kg/h))
(barrel/day) Stream 15 364 3901 1261.1 200.0 Stream 25 416 3901
1261.1 200.0 Stream 240 450 3901 1261.1 206.3 Stream 250 150 3901
1261.1 206.3 Stream 260 153 100 1261.1 206.3 Stream 270 50 1 0.6
0.1 Stream 285 50 1 661.0 100.0 Stream 10 50 1 599.5 106.2
TABLE-US-00004 TABLE 4 Stream properties for Example 1. FIG. 7 FIG.
8 Properties Stream 10 Stream 10 Specific Gravity (API) 34.2 34.4
TBP 5% (deg C.) 35 35 TBP 10% (deg C.) 98 99 TBP 30% (deg C.) 215
184 TBP 50% (deg C.) 337 262 TBP 70% (deg C.) 453 418 TBP 90% (deg
C.) 596 543 TBP 95% (deg C.) 634 611 Sulfur Content (wt %) 2.7 2.6
Nitrogen Content (wt ppm) 925 895 Kinematic Viscosity at 100 F.
(cSt) 1.5 1.4
[0111] The results in Table 4 show that passing the mixed feed
through the convection section of a furnace produces a SCW-treated
product (FIG. 8 stream 10) that is of better quality than the
SCW-treated product from a supercritical water process that does
not integrate a steam cracker (FIG. 7 stream 10). The longer
exposure of the stream to hot temperatures increases the amount of
hydrocarbons that undergo conversion reactions, resulting in more
light fractions.
[0112] Although the present invention has been described in detail,
it should be understood that various changes, substitutions, and
alterations can be made hereupon without departing from the
principle and scope of the invention. Accordingly, the scope of the
present invention should be determined by the following claims and
their appropriate legal equivalents.
[0113] There various elements described can be used in combination
with all other elements described here unless otherwise
indicated.
[0114] The singular forms "a", "an" and "the" include plural
referents, unless the context clearly dictates otherwise.
[0115] Optional or optionally means that the subsequently described
event or circumstances may or may not occur. The description
includes instances where the event or circumstance occurs and
instances where it does not occur.
[0116] Ranges may be expressed here as from about one particular
value to about another particular value and are inclusive unless
otherwise indicated. When such a range is expressed, it is to be
understood that another embodiment is from the one particular value
to the other particular value, along with all combinations within
said range.
[0117] Throughout this application, where patents or publications
are referenced, the disclosures of these references in their
entireties are intended to be incorporated by reference into this
application, in order to more fully describe the state of the art
to which the invention pertains, except when these references
contradict the statements made here.
[0118] As used here and in the appended claims, the words
"comprise," "has," and "include" and all grammatical variations
thereof are each intended to have an open, non-limiting meaning
that does not exclude additional elements or steps.
* * * * *